On Mon, Apr 6, 2020 at 12:02 AM Chris Angelico <ros...@gmail.com> wrote:
> On Mon, Apr 6, 2020 at 1:53 PM Jonathan Goble <jcgob...@gmail.com> wrote: > > > > I'm getting ready to get back into an old personal project with some new > ideas. Before I do, I need to ask a question regarding the stability of > CPython bytecode. Before you say it, I am well aware and fully understand > that the opcodes may change in value and semantics between 3.x and 3.(x+1) > without notice, and that's acceptable to me. > > > > My question is, are the opcodes guaranteed stable across the lifetime of > a single 3.x release? In other words, are they guaranteed to not change > values or semantics between 3.x.y and 3.x.(y+1)? Reading through the list > of opcodes in the dis documentation, it seems that all changes have > occurred in 3.x.0, so it seems the answer would be yes, but then the > "CPython implementation detail" paragraph at the top doesn't specify that > and is a little vague on whether that's true or not. > > > > The best way to look at this is to consider how long a .pyc file is > valid. They're currently named something like > __pycache__/modulename.cpython-38.pyc which is a fairly clear > indication that the cached compiled module should be valid for any > CPython 3.8.x release. So yes, you should be safe within any given > release. The reason it's a CPython implementation detail is also > hinted at in the file name: if you were to use Jython or PyPy or > IronPython or MicroPython or any other implementation, you can't be > sure your bytecodes will work, even if the version number is the same. > (An interpreter can be compatible with Python 3.8 without having the > same bytecode as CPython 3.8.) > > So for your purposes, it sounds like, yes, this WILL work. :) > > ChrisA > Thanks, I never really looked closely at .pyc files, so I missed that. Good to know that I only have to watch for changes between feature releases. I knew that about "CPython implementation detail", that it wouldn't be valid on non-CPython implementations, but didn't clearly state so in the OP. Regardless, I appreciate the reminder.
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